What the "briefings" were like, and why there is confusion.
Several of the books on that period describe the CIA "briefings". The principals were given short notice, not allowed to bring any of their staff, were not allowed to record or take notes, were told the "briefing" was completely secret and then given limited information in general terms.
After the "briefing" they realized they'd been had, that what has happened could happen. Bush & Co. could allege they'd been "briefed", that Congress had been notified, without their having divulged any workable information.
As you've noticed, "plausible deniability" for Conservatives has come to include the most implausible scenarios. All it has to do is obey the laws of physics and it's their reality if it fits what they wasnt to believe.
Arf